Catalytic combustion of lean methane–air mixtures

Sazonov, V. A.; Ismagilov, Z. R.; Prokudina, N. A.

doi:10.1016/s0920-5861(98)00294-6

Cited by 13 publications

(5 citation statements)

References 3 publications

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“…Sazonov et al [12] reported that the reaction rate for methane oxidation only depend on the amount of iron, suggesting that the role of the crystallite size and the dispersion degree of iron oxide is limited. In contrast, Zhang et al [13] observed in toluene oxidation on Fe/SBA-15 catalysts that dispersed iron oxide species were more reducible than aggregated species, and this better dispersion led to higher activity.…”

Section: Introductionmentioning

confidence: 99%

Porous clays heterostructures as supports of iron oxide for environmental catalysis

Sanchis

Cecilia

Soriano

et al. 2018

Chemical Engineering Journal

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Porous Clays Heterostructures (PCH) from natural pillared clays (bentonite with a high proportion of montmorillonite) have been used as supports of iron oxide for two reactions of environmental interest: i) the elimination of toluene (a representative compound of one of the most toxic subsets of volatile organic compounds, aromatics) by total oxidation and ii) the selective oxidation of H 2 S to elemental sulfur. For both reactions these catalysts have resulted to be remarkably more efficient than similar catalysts prepared using conventional silica as a support. Thus, in the total oxidation of toluene it has been observed that the catalytic activity obtained using siliceous PCH is two orders of magnitude higher than that with conventional silica. The catalytic activity has shown to be dependant of the capacity of the support for dispersing iron oxide in a way that the higher the dispersion of iron oxide on the surface of the support, the higher is the activity. In the case of the selective oxidation of H 2 S to S both higher catalytic activity and higher selectivity to S have been observed using siliceous porous clays heterostructures than using conventional silica. Highly dispersed FeOx species have been shown as highly selective towards elemental sulfur whereas more aggregated FeOx species favour the formation of sulphur oxides decreasing the selectivity to S. Analyses of the surface by XPS have shown the predominance of sulfate species in the catalysts presenting low selectivity to elemental sulfur.

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Section: Introductionmentioning

confidence: 99%

Porous clays heterostructures as supports of iron oxide for environmental catalysis

Sanchis

Cecilia

Soriano

et al. 2018

Chemical Engineering Journal

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“…Thus working at 600ºC a remarkable drop in the hydrocarbon conversion with the time on line is reported. In terms of activity, it is reported that the reaction rate for methane oxidation linearly depends on the amount of iron, suggesting that different iron oxide species and iron oxides with distinct crystallite size presents a very similar intrinsic reactivity [14]. Similarly, the total oxidation of lower alkanes has also been studied using iron oxide catalysts [12,15], showing that iron oxide was fairly active for the oxidation of propane and propene at low temperatures although less than manganese oxide [15,16].…”

Section: Introductionmentioning

confidence: 99%

Total oxidation of VOCs on mesoporous iron oxide catalysts: Soft chemistry route versus hard template method

Solsona

Garcı́a

Sanchis

et al. 2016

Chemical Engineering Journal

118

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The total oxidation of two representative VOCs, propane and toluene, has been studied using mesoporous-Fe 2 O 3 catalysts. Different preparation methods have been followed leading to mesoporous materials with different characteristics. Whilst a mesoporous catalyst formed by aggregation of nanocrystals has been produced by soft chemistry using oxalic acid as precipitating agent, a mesoporous material with crystalline walls have been prepared by a nanocasting route using a hard template. These catalysts have been characterized by several physicochemical techniques: XRD, N 2 adsorption, TPR, XPS, TEM, HR-TEM, SAED and EDX. Among the different Fe 2 O 3 catalysts synthesized differences not only in the surface area and morphology have been observed but also in the lattice parameter, in the concentration of oxygen defects for VOCs adsorption and in the reducibility. In the case of the toluene oxidation it has been observed that the catalytic activity is highest for the catalysts prepared by a nanocasting route, which presents a very high surface area of 208 m 2 g-1. Conversely, for propane oxidation the most active catalyst resulted to be the mesoporous nanocrystalline catalyst formed by aggregation. In this case, a direct relationship between reducibility and catalytic activity normalized per surface area has been observed. The differences between toluene and propane oxidation can be tentatively ascribed to different reaction mechanisms to be accounted for.

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“…Aside from its importance as a practical fuel, methane holds an almost unique place as a hydrocarbon fuel, since its detailed combustion chemistry at high temperatures is simple enough so that it can be described at the elementary-step level with a relatively small reaction mechanism compared to higher hydrocarbon fuels (Deutschmann et al, 2000;Westbrook and Dryer, 1981). A supported platinum catalyst is employed in the present work, as platinum-based catalysts have been found to be the most efficient catalysts during combustion (Kuper et al, 1999;Sazonov et al, 1999). For the catalyst 3 washcoat, a mean pore diameter of 20 nm, together with a porosity of 0.5 and a tortuosity factor of 3 are considered.…”

Section: Physical Modelmentioning

confidence: 99%

Combustion and Emissions Characteristics of Methane-Air Mixtures in Catalytic Micro-Combustors: A Computational Fluid Dynamics Study

Chen¹,

Liu²,

Liu³

et al. 2018

Frontiers in Heat and Mass Transfer

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The combustion and emissions characteristics of methane-air mixtures in high-temperature catalytic micro-combustors were studied numerically. Both the heterogeneous and homogeneous chemistry were modeled simultaneously using detailed reaction mechanisms in order to better understand the role of each pathway in determining the product distributions. Computational fluid dynamics simulations were performed at a variety of pressures, temperatures, compositions, and combustor dimensions to determine their effects on the combustion and emissions characteristics. Comparisons were made between the results obtained for a purely heterogeneous case, a purely homogeneous case, and a coupled homogeneousheterogeneous case. It was shown that homogeneous and heterogeneous chemistry take place on similar time-scales with each predicting complete conversion of methane in the system. The contribution of homogeneous and heterogeneous reactions depends strongly upon the operating conditions. The heterogeneous chemistry significantly inhibits the homogeneous chemistry due in part to the radical quenching occurring on the catalytic surfaces, which results in lack of homogeneous chemistry. The inhibiting effect also accounts for the low emissions of nitrogen oxides, as these species are formed by a homogeneous reaction pathway. Nitric oxide is the main nitrogen pollutant formed under lean-burn conditions.

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Catalytic combustion of lean methane–air mixtures

Cited by 13 publications

References 3 publications

Porous clays heterostructures as supports of iron oxide for environmental catalysis

Porous clays heterostructures as supports of iron oxide for environmental catalysis

Total oxidation of VOCs on mesoporous iron oxide catalysts: Soft chemistry route versus hard template method

Combustion and Emissions Characteristics of Methane-Air Mixtures in Catalytic Micro-Combustors: A Computational Fluid Dynamics Study

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